1. Field of the Invention
This invention relates to the construction of an article of footwear and more specifically to a cushioning construction for the sole of an article of footwear.
2. Background of the Invention
The human foot is a complex and remarkable piece of machinery, capable of withstanding and dissipating many impact forces. The natural padding of fat at the heel, as well as the collapsibility of the arch, help to cushion the foot. Throughout the course of an average day, the feet and legs of an individual are subjected to substantial impact forces. Running, jumping, walking, and even standing exert forces upon the feet and legs of an individual which can lead to soreness, fatigue, and injury.
Although the human foot possesses natural cushioning and rebounding characteristics, the foot may need extra support to overcome many of the forces encountered during extended periods of activity. Unless an individual is wearing shoes which provide proper cushioning and support, the soreness and fatigue resulting from even low levels of activity on unnatural surfaces is acute, and its onset accelerated. The discomfort for the wearer that results may diminish the incentive for further activity. Equally important, inadequately cushioned footwear can lead to injuries such as blisters; muscle, tendon and ligament damage; and bone stress fractures. Improper footwear can also lead to other ailments, including back pain.
In light of these problems, numerous attempts have been made to incorporate into the sole of a shoe improved cushioning and resiliency. For example, attempts have been made to enhance the natural elasticity and energy return of the foot by providing shoes with soles which store energy during compression and return energy during expansion. These attempts have included the formation of shoe soles that include springs, gels or foams. However, these solutions are expensive, and tend to lose their effectiveness over time.